how to make an oval panel 3" smaller than tabletop?

[Scott Gilroy]

I have an oval table top that needs a plywood base for additional support. I need to cut a large oval to match the tabletop, but 3" smaller all around.

Any suggestions on how to replicate the oval, only 3" smaller all around?
Thanks for the input,
Scott

[Brice Burrell]

Tracing with a compass is one way, another is layout a new smaller one. Throw your numbers in here and you're all set.

http://www.blocklayer.com/ovaleng.aspx

[Jamie Buxton]

Saber saw.

I must not be understanding something here. What's the problem?

[Mike Heidrick]

block of wood, thin strip nailed to block that will reach 3" inside table diameter, paper or thin hardboard on table to draw on, pencil in strip of wood, block moves around table edge, pencil traces shape. Something like that.